Radiation transmittance (ratio of transmitted to incident radiation) through clear ice, refrozen slush ice, and brash ice, from ice surface to ice-water interface in the 400 to 600 nanometer range (photosynthetically active range), was measured at two freshwater lakes: Silver Lake, near Ann Arbor, Michigan and Whitefish Point on Lake Superior. Data available include surface and under-ice sensor readings, date and time of observation, ice thickness, water depth, distance of under-ice sensor from ice bottom surface, and site number/location.